Wisconsin's New Growing Zone Map

Wisconsin's New Growing Zone Map

Part of Ep. 2104 Climate Change for Gardeners

We talk about how climate change will affect the future for gardeners, but it's already here. Dr. Laura Jull introduces the new U.S.D.A. Plant Cold Hardiness Zone Map for Wisconsin from the D.C. Smith Greenhouse on the University of Wisconsin-Madison campus.

Premiere date: May 22, 2013

TRANSCRIPT+
Wisc Gardener Transcript: 

Shelley Ryan:

Isn't this lush and tropical looking? It's not what Wisconsin looks like yet and let's hope it's not going to be that way for a while. We are at DC Smith Greenhouse on the UW-Madison campus. I'm with Dr. Laura Jull, woody, ornamental plant specialist for the UW-Extension. 2012 has been an exciting year for woody plant lovers in many ways. We have a couple new things to talk about.

 

Laura Jull:

Yeah, Shelley. We have a new USDA plant cold-hardiness zone map. This new map was put out by USDA agriculture research service as well as Oregon State University. It's based on 30 years' worth of data. It's more accurate than the previous map because there are more weather stations involved throughout the country that were used as well as it takes into account GIS technology and differences in elevation and grade changes. So it's a lot more accurate. You can actually type in your zip code. It will tell you specifically what your cold hardiness zone is for your area.

 

Shelley Ryan:

That's kind of neat. I've always argued that I'm colder than Madison. I can actually look it up on the map and prove it, or find out that I'm totally wrong! Now the biggest question is has this map changed from the previous one?

 

Laura Jull:

Yes, it has, actually. In fact, most of Wisconsin is one-half cold hardiness zone warmer than it was.

 

Shelley Ryan:

Warmer.

 

Laura Jull:

Yes. Previously, south-central Wisconsin was zone 4b. Now we're zone 5a. But I wouldn't run out to the store and try to grow bananas in your yard.

 

Shelley Ryan:

Would you take this as an indication of climate change since it's over a 30-year period of studies?

 

Laura Jull:

Yeah, I would. I mean, we're definitely getting warmer. There's no question about that. As gardeners, we need to adjust accordingly. Selecting plants that are more heat tolerant as well as drought tolerant as well as non-invasive and pest resistant. That's really important. This year, I actually did my own personal evaluations and I was amazed at what plants really did well through this drought.

 

Shelley Ryan:

The year of the drought of 2012 we learned something good from?

 

Laura Jull:

Yep, we actually did. There are a number of plants that I saw that were very drought tolerant. Some of our natives like Kalm's St. John's wort, Hypericum. The other one is Aronia, or chokeberry.

 

Shelley Ryan:

Highly ornamental and edible.

 

Laura Jull:

Another one was our native Eastern Ninebark especially the dwarf, or the purply cultivars. They're quite drought tolerant. Weigela is another one that's not native but it showed great drought tolerance, as well. And a number of other plants.

 

Shelley Ryan:

In any case, even though we're a half zone warmer you also said, don't just run out and buy the first thing you see that's half a zone warmer. Do some research, be intelligent. Something I hear again and again is "buy local."

 

Laura Jull:

Yeah, I'm a big fan of buying local from local nurseries or garden centers that either grow their own plants, or buy local plants and then sell them. Some of the big box stores that I've actually been into are selling plants that really aren't cold hardy here. They actually have regional buyers and they buy for the entire Midwest. The Midwest includes about four or five different cold hardiness zones.

 

Shelley Ryan:

Right, it's a big area.

 

Laura Jull:

Yeah, and so I always say, buyer beware. Do some research on your own, looking plants up. But if you buy from a local nursery source they know what's really hardy or not.

 

Shelley Ryan:

\Even buying local you talked about drought tolerant plants some of these that are really drought tolerant. If we don't establish them well they're still going to just curl up and die.

 

Laura Jull:

Yes, you have to make sure they're well established before they're truly drought tolerant. Even some of the most drought tolerant plants if you don't water them in the first couple of years on a regular basis, they will die.

 

Shelley Ryan:

A tree needs two or three years to get established then it can be drought tolerant.

 

Laura Jull:

Yeah, it depends on the size of the tree. For this part of the country, generally one-inch caliber tree, or the diameter of the tree when you plant it equals one year of time it needs to be able to establish. For shrubs it's about the same, two to three years.

 

Shelley Ryan:

Okay, we'll have a list of these plants that you learned about in 2012. People need to remember to water let them get established and buy local.

 

Laura Jull:

Absolutely.

 

Shelley Ryan:

Just like we do with our food. Thanks, Laura.

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